Conventionally, a system, in which a gear subassembly is configured as a single component, is widely known for an exhaust gas recirculation system (hereinafter referred to as an EGR system) that recirculates exhaust gas discharged from an internal combustion engine into an intake-air passage (see, for example, JP-A-2010-190116 corresponding to US2010/0206274A1).
A system provided with a turbocharger that rotates an exhaust turbine by exhaust gas and compresses intake air through a compressor coaxial with the exhaust turbine is known for an air intake and exhaust system of the engine. In the air intake and exhaust system equipped with the turbocharger, the EGR system recirculates exhaust gas into an intake passage mainly through a low-pressure EGR passage that communicates between an exhaust passage on a downstream side of the exhaust turbine in an exhaust gas flow direction, and the intake passage on an upstream side of the compressor in an intake air flow direction.
The EGR system includes an EGR valve that changes an opening degree of the low-pressure EGR passage so as to increase or decrease the amount of exhaust gas recirculated, an electric motor that generates output for driving the EGR valve, reduction gears that decelerate the output of the electric motor to transmit it to the EGR valve, an intake throttle valve that reduces a flow of intake air in the intake passage on an upstream side of an exhaust-gas merging part in the intake air flow direction, and a link mechanism that synchronizes movement of the intake throttle valve with movement of the EGR valve.
The gear subassembly is configured, for example, by integrating a gear that is a part of the reduction gears and is fastened to a rotatable shaft of the EGR valve, and a cam having a cam profile that is a part of the link mechanism and shows a synchronization pattern of the intake throttle valve relative to the EGR valve, and the subassembly thereby serves as one component of the EGR system. Recent demand for high fuel efficiency of a vehicle is extremely great. To cope with such demand for fuel efficiency, request for weight saving of the gear subassembly becomes high, too.